The present invention relates to a sensor arrangement, in particular for a high-pressure sensor.
For example, DE 196 03 674.7 A1 has disclosed a pressure sensor in which the signal detection is executed by means of a pressure detector made of stainless steel, in which a resistance measuring bridge is disposed on the side of a measuring diaphragm oriented away from the measurement medium, for example using the thin-film technique. Movements of the measuring diaphragm due to pressure changes in the measurement medium therefore lead to compressions or elongations of the resistance bridges and therefore to resistance changes in the respective resistors. This resistance change and the signal amplification are utilized by an electronic evaluation circuit, which is disposed on a printed circuit board.
In this instance, the contacting of the pressure detector with the evaluation circuit is produced by means of a soldered, flexible foil strip conductor or optionally also by means of an additional intermediate member, a so-called spacer. By means of bonded connections, the pressure detector contacts this spacer and the evaluation circuit disposed on the spacer is soldered in place. The contacting of the evaluation circuit with the connector attached to the sensor unit is produced either by means of soldered, flexible lines or directly by means of connector pins, which are sealed in the transition to the housing of the sensor arrangement by means of soft rubber.
In the manufacture of a pressure sensor of this kind, an inexpensive, structurally simpler sensor design should be provided, which is suitable for high vibrational stresses and temperature stresses and for high-pressure measurement in aggressive mediums such as oil, diesel, gasoline, or brake fluid in motor vehicles.
U.S. Pat. No. 5,656,780 has disclosed a sensor arrangement that includes a pressure detector. Electronic sensor structures are produced on the underside of an insulator substrate, which is inserted into the housing of the sensor arrangement. A hybrid circuit is disposed on the top side of the insulator substrate and contacts the sensor structures on the underside by means of through contacts. The insulator substrate is placed with the sensor structures onto the measuring diaphragm.
The sensor arrangement in the modification according to the invention is advantageous in that the evaluation circuit, as a hybrid circuit, can be fastened directly to the sensor circuit, i.e. to the measuring bridge on the measuring diaphragm, thus produce electrical connections between the evaluation circuit and the sensor circuit and a ground connection to the housing of the sensor arrangement.
According to a particularly advantageous embodiment, the contacting of the connections of the hybrid circuit with the connector pins of the connector in the sensor arrangement can be produced by means of pressure contacts. The pressure contacts can simply be either S-shaped leaf springs or helical compression springs; the helical springs are guided in a sleeve that serves as a retainer and is disposed on either the hybrid circuit or the connector.
The electronic evaluation circuit according to the invention is produced using intrinsically known hybrid technology, e.g. as an ASIC, and can be connected by means of a glue connection, directly to a detector that supports the measuring diaphragm. The necessary electrical connection to the housing ground of the sensor arrangement is advantageously produced without additional components. Required soldering or bonding processes can therefore be eliminated since the electrical connections can be produced at the same time as the fastening of the hybrid circuit. In addition, the flexible foils required in the prior art or an intermediate member, a so-called spacer, are not necessary here, which represents a considerable cost savings.
Other advantages of the arrangement according to the invention are the very short and symmetrical electrical connections between the measuring bridge and the evaluation circuit. This achieves a very favorable compatibility with electromagnetic irradiation. The resulting compact design reduces not only the number of electrical connecting elements, but also the number of possible failure sources, which extends the service life of the sensor arrangement. In addition, the compact design has fewer oscillation-prone mechanical parts and the sensor arrangement is more able to withstand vibration.
The helical compression springs or the S-shaped leaf springs permit a simple, automated assembly of the connector.
It is particularly advantageous if the pressure detector is mounted on a multi-part pressure fitting in which the detector is first fastened to a threaded fitting, which can be screw connected to a subassembly for the introduction of the measurement medium. The threaded fitting is connected to a base housing.
The thus divided pressure fitting, in which the base body and the threaded fitting can be produced separately, achieves a smaller overall height of the sensor arrangement since the pressure detector can initially be welded radially to the threaded fitting, without the base body. It is therefore less expensive to produce the pressure fitting and the threaded fitting requires considerably less cutting work than in the one-piece embodiment.
It is also advantageous if the threaded fitting is then welded to the base housing at its threaded end. The base housing here can easily be embodied as a hexagonal housing, which is advantageous for the installation on a subassembly; either a milled or a particularly inexpensive deep-drawn part can be used for this. A hexagonal housing of this kind can be comprised of weaker and therefore less expensive material than the pressure fitting. In addition, the consequently produced metallic encasing of the evaluation circuit means that an improved EMV behavior of the sensor arrangement can be expected; this is particularly advantageous with small signal strokes of the pressure detector.
On the whole, the partite pressure fitting minimizes an introduction of mechanical stress into the detector and therefore a signal drift due to the starting torque, and the separate base housing makes it possible to use a shorter connector made of plastic, which improves its mechanical connection and therefore improves the capacity of the entire arrangement to withstand vibration.
The sensor arrangement can preferably be a high-pressure sensor for detecting the pressure of oil, diesel, gasoline, or brake fluid in a motor vehicle.
These and other features of preferred modifications of the invention ensue from not only the claims, but also from the specification and the drawings, in which the individual features can each be realized in and of themselves or united in various sub-combinations in the embodiment of the invention and in other fields and can also prove to be advantageous for intrinsically patentable embodiments, for which protection is hereby claimed.